Abstract

From the time of conception until the time of death, the path of the human organism is created and shaped by decisions. Some decisions we make ourselves, some are made for us; some will make us, some will break us. What most decisions have in common, however, is that they are made under risk, that is, without complete information regarding the potential decision outcomes. One interesting feature about decisions under risk is variability: different individuals make different choices, and even the same individual may, given repeated occasions, make different choices. This doctoral thesis aims to address the issue of individual differences by looking at several specific variables which may impact inter- and intra-individual differences in risk taking, namely age, the measures used to assess risk-taking, neural function and neural structure. In a set of four studies, the following questions were addressed: (1) To what extent do life span trajectories of risk taking change as a function of whether self-report or behavioral measures are used to assess risk taking? (2) Do younger and older individuals differ in the neural functional representation of risk and reward? (3) Do the neural representations of described and experienced risk converge, both at group and individual level? To what extent is neural function predictive of risky choice? (4) To what extent do individual differences in neural structure explain variance in psychometrically derived risk preference factors? The main findings are: (1) Self-report and behavioral measures of risk taking do not converge and lead to different life span trajectories. (2) The ventromedial prefrontal cortex is differentially activated in younger and older adults, with activation differences possessing differential explanatory power for choice in the two age groups. (3) Described and experienced risks show convergence at group level, divergence at the individual level, and are differentially predictive of risky choice. (4) Neural structural indices explain variance in the general risk preference factor, but not domain-specific risk preference factors. Based on the findings from all four studies, this thesis provides corroborating evidence for the argument that not all risk-taking measures are created equal and that a taxonomy of risk-taking measures and their respective cognitive and affective demands is required to understand individual differences in risk taking.